A study of aphid-fighting pesticides has revealed that organic products can sometimes be more environmentally harmful than synthetic products.

Many people take it for granted that organic pesticides are more eco-friendly. There’s also a “fundamental misconception that organic farms do not use pesticides,” researchers write in PLoS ONE. Organic farming practices do allow the application of pesticides, the team says, as long as no synthetic chemicals are used.

The authors tested six insecticides intended to protect soybean crops from aphids, including both synthetic and organic options. The two organic pesticides were the least effective at aphid control, the team reports. They were also less selective in the field and tended to kill a greater number of the aphids’ natural predators along with the aphids.

The organic products had among the highest environmental impact per application, in part because large amounts had to be used. Instead of assuming that organic pesticides are always more sustainable, the researchers say, policymakers should consider the performance of individual treatments. – Roberta Kwok